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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Wildlife and Fisheries Science

First Advisor

Steven R. Chipps


largmouth bass, food, predation, lactate dehydrogenase


Optimal foraging theory predicts that predators choose prey based on size, morphology, and behavior that maximizes the net energy gained per time spent foraging. For prey choice to be optimal, the ratio of energy gained to energy expended should be maximized. Activity costs associated with pursuit and capture are substantial and considered to be the most costly activity in free-swimming fish. Foraging behavior and fish activity have been linked to production of glycolytic (anaerobic) enzymes such as lactate dehydrogenase (LDH), in the axial, white musculature of fish. To examine the effect of prey size on anaerobic activity, I conducted a series of laboratory feeding trials with largemouth bass (Micropterus salmoides) predators (240-303 mm total length [TL]) and bluegill (Lepomis macrochirus) prey (35-80 mm). Prey selectivity trials, conducted in 900-L mesocosms, indicated that small to moderate sized prey (35 to 50 mm) were preferred (88.4%) over larger (60-85 mm) individuals (11.5%). Activity cost, as indexed by LDH, increased in largemouth bass with increasing prey size; LDH activity was 20% higher in bass feeding on large compared to small prey. Moreover, bioenergetics modeling revealed that consumption was appreciably under-estimated for larger prey sizes (65-80 mm), implying that activity costs increase for larger prey, consistent with LDH measurements. In separate experiments evaluating effects of vegetation density, I found no differences in anaerobic (LDH) activity levels among bass feeding on similar-size prey. However, largemouth bass growth was significantly greater in low vegetation compared to high vegetation treatments. Moreover, conversion efficiencies for largemouth bass were lower in high vegetation treatments, implying that aerobic activity costs are higher for fish foraging in highly vegetated environments.

Library of Congress Subject Headings

Largemouth bass -- Food
Predation (Biology)
Lactate dehydrogenase


Includes bibliographical references (page 45-53)



Number of Pages



South Dakota State University


Copyright © 2004 Trevor M. Selch. All rights reserved.